1. Field of the Invention
The invention relates to an electron beam apparatus provided with an electron source, an electron optical system registered about an optical axis of the apparatus, and an energy selective device for spectrometric measurement. The invention also relates to an energy selective device for use in such an apparatus.
2. Description of the Related Art
An apparatus of this kind is known from U.S. Pat. No. 4,812,652issued Mar. 12, 1989. It is an object of the known apparatus to combine specimen imaging and local sensitive spectrometric measurements on a specimen in a transmission electron microscope. Thus spectrometric measurements should not hamper imaging action of the microscope, and vice versa. The energy dispersive device used in the known apparatus comprises (see FIG. 2 of said patent) a first beam bending prism, a beam reflector and a second beam bending prism. An electrostatic mirror is necessary in order to bring the electrom beam back in line with the optical axis of the apparatus after leaving the dispersive device. The device has as a drawback a limited isochromatic field of the view, which limits the dimensions of a specimen to be investigated per specimen position. A further drawback of the known apparatus is that due to the electrostatic mirror it can only be used with restricted high voltage values and that it is rather sensitive to external field strength disturbances.